Traffic proximity studies show significant chronic childhood respiratory health effects from living or going to school near traffic, but no one has yet been able to determine which pollutant component(s) are responsible for these effects. The objective of Dr. Fruin's research is to provide a novel approach to exposure assessment for air pollution chronic disease epidemiology, using highly time- and spatially-resolved mobile measurements of ultrafine particles, particle-bound PAHs, coarse PM, and NO2, likely causal pollutants which show sharp- but not identical-near-road concentration gradients. The proposed sampling platform (housed in a hybrid electric vehicle) will permit spatial and diurnal characterization of dynamic exposures not currently possible using fixed-location monitoring. Associations of time-of-day and location-specific exposures at school and home with bronchitic symptoms, wheeze and asthma (the most common chronic childhood disease) will be examined. The research will be conducted in a large cohort of the University of Southern California Children's Health Study (CHS), an influential longitudinal study of the health effects of air pollution on children, which has followed over 11,000 children from kindergarten through high school. The CHS is a rich source of existing health and exposure data, conducted by a talented research team with a productive history of findings that have greatly advanced our understanding of air pollution effects. Dr. Scott Fruin joined this team in the Department of Preventive Medicine at USC in 2007 as assistant professor in the Environmental Health Division, which has conducted the CHS since 1992. Dr. Fruin received his doctorate in 2003 from UCLA's School of Public Health while working at the California Air Resources Board. The goal of this five-year development award is to provide Dr. Fruin with the skills and expertise to become an independent researcher in the field of air pollution exposure assessment as he gains the essential expertise to integrate improved exposure assessment techniques into large epidemiological studies like the CHS. His career development plan will build: 1) improved expertise in spatial statistics and geographic information systems (GIS) tools, to be able to effectively build spatio-temporal exposure models from the new measurement techniques; 2) improved understanding of respiratory health endpoints; and 3) improved expertise in environmental epidemiology, to link respiratory health endpoints to the improved exposure estimates. Dr. Fruin will take coursework and receive mentoring from experts in each of these fields while applying new expertise directly as he conducts an ambitious field study in Years One and Two. Three highly-qualified mentors will supervise his training. Rob McConnell (environmental epidemiology) will serve as the primary mentor, while Ed Avol (exposure assessment) and Dr. Jim Gauderman (spatial biostatistics) will serve as co-mentors. Additional advisors and CHS investigators will also enhance this collegial and highly productive research environment that is ideal for a new investigator to develop the multi-disciplinary skills that are the objective of this proposal.